U.S. patent number 10,560,004 [Application Number 15/678,715] was granted by the patent office on 2020-02-11 for sensor magnet holder, magnet fixing structure, and motor.
This patent grant is currently assigned to MABUCHI MOTOR CO., LTD.. The grantee listed for this patent is Mabuchi Motor Co., Ltd.. Invention is credited to Satoshi Kikuchi, Kazuyuki Yamamoto.
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United States Patent |
10,560,004 |
Yamamoto , et al. |
February 11, 2020 |
Sensor magnet holder, magnet fixing structure, and motor
Abstract
A sensor magnet holder is used to fix a sensor magnet to a motor
shaft. The sensor magnet holder includes a press fitting part to
which the motor shaft is press fitted; a holding part provided
radially outside the press fitting part to hold the sensor magnet;
and a joint part that joins the press fitting part and the holding
part. The joint part is configured such that at least a part of the
joint part is deflected by an external force.
Inventors: |
Yamamoto; Kazuyuki (Matsudo,
JP), Kikuchi; Satoshi (Matsudo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Mabuchi Motor Co., Ltd. |
Matsudo, Chiba |
N/A |
JP |
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Assignee: |
MABUCHI MOTOR CO., LTD.
(Matsudo, Chiba, JP)
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Family
ID: |
56688805 |
Appl.
No.: |
15/678,715 |
Filed: |
August 16, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170346372 A1 |
Nov 30, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2016/052134 |
Jan 26, 2016 |
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Foreign Application Priority Data
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Feb 20, 2015 [JP] |
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2015-031974 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K
11/215 (20160101); H02K 7/1166 (20130101) |
Current International
Class: |
H02K
11/215 (20160101) |
Field of
Search: |
;310/68B,75R,83
;324/207.2,207.25 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102801251 |
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Nov 2012 |
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CN |
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2006-180580 |
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Jul 2006 |
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JP |
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2006-180580 |
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Jul 2006 |
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JP |
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2010-035411 |
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Feb 2010 |
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JP |
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2012-016235 |
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Jan 2012 |
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JP |
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2012-016235 |
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Jan 2012 |
|
JP |
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2012-244851 |
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Dec 2012 |
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JP |
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2014-200128 |
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Oct 2014 |
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JP |
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Other References
Notification of Reasons for Refusal for Japanese Application No.
2015-031974 dated Jun. 20, 2018; 7 pages including English
translation. cited by applicant .
First Notice of Reason for Refusal for Chinese Application No.
2016800104205 dated Dec. 12, 2018; 11 pages including English
translation. cited by applicant .
Patent Cooperation Treaty: International Preliminary Report on
Patentability for PCT/JP2016/052134 dated Apr. 19, 2016; 12 pages
including English translation. cited by applicant .
Patent Cooperation Treaty: International Search Report for
PCT/JP2016/052134 dated Apr. 19, 2016; 5 pages including English
translation. cited by applicant .
The State Intellectual Property Office of People's Republic of
China--Second Office Action in CN App. No. 201680010420.5 dated
Jul. 16, 2019; 15 pages including English translation. cited by
applicant .
Notice of Refusal for Japanese Application No. 2015-031974 dated
Nov. 30, 2017; 6 pages including English translation. cited by
applicant.
|
Primary Examiner: Mullins; Burton S
Attorney, Agent or Firm: Schwabe Williamson & Wyatt,
PC
Claims
The invention claimed is:
1. A sensor magnet holder used to fix a sensor magnet to a motor
shaft, comprising: a press fitting part to which the motor shaft is
press fitted; a holding part provided radially outside the press
fitting part to hold the sensor magnet; and a joint part that joins
the press fitting part and the holding part, comprising: a radial
part that extends radially outward from the press fitting part; and
a circumferential part that extends in a circumferential direction
from an end of the radial part opposite to the press fitting part,
wherein the joint part is configured such that at least a part of
the joint part is deflected by an external force.
2. The sensor magnet holder according to claim 1, wherein the
circumferential part comprises: a first circumferential part
extending in one circumferential direction from the radial part;
and a second circumferential part extending in the other
circumferential direction from the radial part.
3. The sensor magnet holder according to claim 1, wherein the joint
part comprises a first joint part and a second joint part at
different positions in the circumferential direction, and the
circumferential part of the first joint part and the
circumferential part of the second joint part are spaced apart from
each other.
4. The sensor magnet holder according to claim 1, wherein the
holding part is provided near an end of the circumferential
part.
5. The sensor magnet holder according to claim 1, wherein the joint
part comprises a first joint part and a second joint part at
different positions in the circumferential direction, and the
circumferential part of the first joint part and the
circumferential part of the second joint part are joined.
6. The sensor magnet holder according to claim 5, wherein the
holding part is provided in a region in which the circumferential
part of the first joint part and the circumferential part of the
second joint part are joined.
7. The sensor magnet holder according to claim 1, wherein a total
of 2n+1 (n is an integer equal to or more than 1) joint parts are
provided at equal intervals in the circumferential direction.
8. The sensor magnet holder according to claim 7, wherein the
holding part is provided opposite to the radial part, sandwiching
the press fitting part.
9. A magnet fixing structure comprising: an annular sensor magnet;
and the sensor magnet holder according to claim 1 mounted to the
center of the sensor magnet, wherein the sensor magnet holder is
configured such that the press fitting part and the holding part
are at least partially contained within the sensor magnet when the
sensor magnet holder mounted to the sensor magnet is viewed in a
direction perpendicular to an axis that runs through a center of
the sensor magnet holder.
10. A motor comprising: a rotor in which a shaft is fixed at the
center; and the magnet fixing structure according to claim 9,
wherein the magnet fixing structure is configured such that the
shaft is press fitted to the press fitting part.
Description
This application is based upon and claims the benefit of priority
from the prior Japanese Patent Application No. 2015-031974, filed
on Feb. 20, 2015, and International Patent Application No.
PCT/JP2016/052134, filed on Jan. 26, 2016, the entire content of
each of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a holder used for a sensor
magnet.
2. Description of the Related Art
In the related art, rotation detectors for detecting a rotational
speed and rotational position are used in small motors. In a
rotation detector, magnets called sensor magnets in which magnetic
poles are alternately formed in the circumferential direction are
fixed to the motor shaft and a magnetically sensitive device is
provided in the neighborhood of the magnets. The sensor magnet is
magnetized such that the magnetic flux varies in accordance with
the rotation of the rotor. Variation in the magnetic pole position
of the sensor magnet detected by the magnetically sensitive device
and accompanying the rotation of the motor shaft corresponds to
variation in the rotational position of the rotor.
It is therefore necessary to fix the sensor magnet to the motor
shaft. One approach to fix the sensor magnet to the motor shaft is
to press fitting the motor shaft to the center of the sensor magnet
directly. However, this method may crack the sensor magnet. An
alternative method of fixing the sensor magnet to the motor shaft
is proposed whereby the sensor magnet is fixed to the motor shaft
via a sensor magnet holder (see JP2010-35411).
The sensor magnet holder according to this method includes a
cylindrical part formed with a press fitting part to which the
motor shaft is press fitted and a plurality of plate-shaped snap
fits projecting from the cylindrical part in an axial direction,
where the cylindrical part and the snap fits are formed as one
piece. The sensor magnet is fixed to the magnet holder by the
plurality of snap fits that are elastically deformed. For this
reason, the stress from the motor shaft generated when the motor
shaft is press fitted to the sensor magnet holder is not directly
transmitted to the sensor magnet so that the likelihood of
occurrence of a crack in the sensor magnet is reduced.
However, since the snap fits of the aforementioned sensor magnet
holder are formed to project axially from the cylindrical part
formed with the press fitting part, the axial length of the sensor
magnet holder is relatively long. This increases the length of the
motor shaft necessary to attach the sensor magnet holder.
Accordingly, further improvements are necessary in order to reduce
the size of the motor, and, in particular, the length of the motor
shaft.
SUMMARY OF THE INVENTION
The present invention addresses the aforementioned issue, and a
purpose thereof is to provide a technology of reducing the size of
a sensor magnet holder for fixing a sensor magnet to a shaft.
A sensor magnet holder according to an embodiment of the present
invention is used to fix a sensor magnet to a motor shaft and
includes: a press fitting part to which the motor shaft is press
fitted; a holding part provided radially outside the press fitting
part to hold the sensor magnet; and a joint part that joins the
press fitting part and the holding part. The joint part is
configured such that at least a part of the joint part is deflected
by an external force.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments will now be described by way of examples only, with
reference to the accompanying drawings which are meant to be
exemplary, not limiting and wherein like elements are numbered
alike in several Figures in which:
FIG. 1 is a sectional view of a motor with a worm reducer according
to the embodiment provided with a rotation detector;
FIG. 2A is a perspective view of the sensor magnet holder according
to the embodiment, and FIG. 2B is a perspective view of the sensor
magnet holder according to the embodiment viewed in a direction
different from that of FIG. 2A;
FIG. 3 is a front view of the sensor magnet holder according to the
embodiment;
FIG. 4 is a sectional view along A-A of the sensor magnet holder
shown in FIG. 3;
FIG. 5 is a sectional view along B-B of the sensor magnet holder
shown in FIG. 3;
FIG. 6 is a rear view of the sensor magnet holder according to the
embodiment;
FIG. 7A is a side view of the sensor magnet holder shown in FIG. 3
viewed in direction C, FIG. 7B is a side of the sensor magnet
holder shown in FIG. 3 viewed in direction D, and FIG. 7C is a side
view of the sensor magnet holder shown in FIG. 3 viewed in
direction E;
FIG. 8A is a perspective view of the sensor magnet according to the
embodiment, and FIG. 8B is a perspective view of the sensor magnet
according to the embodiment viewed in a direction different from
that of FIG. 8A;
FIG. 9 is a front view of the sensor magnet according to the
embodiment;
FIG. 10 is a sectional view along F-F of the sensor magnet holder
shown in FIG. 9;
FIG. 11 is a rear view of the sensor magnet according to the
embodiment;
FIG. 12A is a perspective view of the magnet fixing structure
according to the embodiment, and FIG. 12B is a perspective view of
the magnet fixing structure according to the embodiment viewed in a
direction different from that of FIG. 12A;
FIG. 13 is a front view of the magnet fixing structure according to
the embodiment;
FIG. 14 is a sectional view along G-G of the magnet fixing
structure shown in FIG. 13;
FIG. 15 is a front view of the sensor magnet holder according to
the first variation;
FIG. 16 is a front view of the sensor magnet holder according to
the second variation;
FIG. 17 is a front view of the sensor magnet holder according to
the third variation;
FIG. 18 is a front view of the sensor magnet holder according to
the fourth variation;
FIG. 19 is a front view of the sensor magnet holder according to
the fifth variation;
FIG. 20 is a front view of the sensor magnet holder according to
the sixth variation;
FIG. 21 is a front view of the sensor magnet holder according to
the seventh variation;
FIG. 22 is a front view of the sensor magnet holder according to
the eighth variation;
FIG. 23 is a front view of the sensor magnet holder according to
the ninth variation; and
FIG. 24 is a front view of the sensor magnet holder according to
the tenth variation.
DETAILED DESCRIPTION OF THE INVENTION
A sensor magnet holder according to an embodiment of the present
invention is used to fix a sensor magnet to a motor shaft and
includes: a press fitting part to which the motor shaft is press
fitted; a holding part provided radially outside the press fitting
part to hold the sensor magnet; and a joint part that joins the
press fitting part and the holding part. The joint part is
configured such that at least a part of the joint part is deflected
by an external force.
According to this embodiment, the sensor magnet holder can be
thinner than otherwise because the press fitting part and the
holding part are not aligned in the axial direction of the motor
shaft. Further, the holding part is capable of holding the sensor
magnet in a stable manner as a result of the joint part being
deflected. By designing the joint part as appropriate, the holding
part is prevented from biasing the sensor magnet with an
unnecessarily large force.
The joint part may include a radial part that extends radially
outward from the press fitting part, and a circumferential part
that extends in a circumferential direction from an end of the
radial part opposite to the press fitting part. In this way, the
joint part can be formed without extending it in the axial
direction. Further, as compared with a case of providing the joint
part extending in the axial direction of the motor shaft, a desired
length of the circumferential part can be secured without requiring
an excessive thickness of the holder. The direction in which the
parts extend needs not to be perpendicular to the axial direction
of the motor shaft. A slight inclination (e.g., 30.degree. or less)
may be provided.
The circumferential part may include: a first circumferential part
extending in one circumferential direction from the radial part;
and a second circumferential part extending in the other
circumferential direction from the radial part. In this way, a
plurality of holding parts can be provided for one joint part.
The joint part may include a first joint part and a second joint
part at different positions in the circumferential direction, and
the circumferential part of the first joint part and the
circumferential part of the second joint part may be spaced apart
from each other. In this way, one of the ends of the
circumferential part becomes a free end so that each
circumferential part can function as a cantilever spring.
The holding part may be provided near an end of the circumferential
part. This can increase the amount of displacement of the holding
part.
The joint part may include a first joint part and a second joint
part at different positions in the circumferential direction, and
the circumferential part of the first joint part and the
circumferential part of the second joint part may be joined. This
allows a part of the joint part to be deflected with a relatively
simple structure.
The holding part may be provided in a region in which the
circumferential part of the first joint part and the
circumferential part of the second joint part are joined.
A total of 2n+1 (n is an integer equal to or more than 1) joint
parts may be provided at equal intervals in the circumferential
direction. In this way, the sensor magnet holder can hold the
sensor magnet in a well-balanced manner.
The holding part may be provided opposite to the radial part,
sandwiching the press fitting part. This prevents the plurality of
radial parts from being aligned in a line in the sensor magnet
holder.
Another embodiment of the present invention relates to a magnet
fixing structure. The magnet fixing structure includes: an annular
sensor magnet; and the sensor magnet holder mounted to the center
of the sensor magnet. The sensor magnet holder is configured such
that the press fitting part and the holding part overlap the sensor
magnet when the sensor magnet holder mounted to the sensor magnet
is viewed in a radial direction. This can realize a thin magnet
fixing structure.
A motor may include: a rotor in which a shaft is fixed at the
center; and the magnet fixing structure. The magnet fixing
structure may be configured such that the shaft is press fitted to
the press fitting part. This reduces transmission of a force
generated when the motor shaft is inserted into the press fitting
part to the holding part, preventing a crack in the sensor magnet
due to an excessive biasing force.
Optional combinations of the aforementioned constituting elements,
and implementations of the invention in the form of methods,
apparatuses, and systems may also be practiced as additional modes
of the present invention.
According to the embodiment, the size of the magnet holder can be
reduced.
A description will be given of an embodiment of the present
invention with reference to the drawings. Like numerals represent
like elements so that the description will be omitted accordingly.
The structure described below is by way of example only and does
not limit the scope of the invention.
The technology of the present invention can be applied to all types
of small motors like brushless motors and motors with a reducer in
which it is required to detect a rotational speed and rotational
position. The description below relates to a case where the
technology is applied to motors with a worm reducer.
(Motor with Reducer)
FIG. 1 is a cross sectional view of a motor with a worm reducer
according to the embodiment provided with a rotation detector. A
motor 10 with a reducer includes a motor unit 12 and a reducer unit
14. The motor 10 with a reducer is an ordinary brushed DC motor.
The motor unit 12 includes a motor case 16 formed by a metallic
material into a shape of a bottomed cylinder and fitted with a
magnet on the inner circumferential surface thereof, and an end
bell 18 attached to the motor case 16 so as to close the opening of
the motor case 16. The end of a motor shaft 20 extending outside
from the end bell 18 of the motor unit 12 is pivotally supported by
a bearing 24 provided inside a reducer case 22.
The reducer unit 14 is comprised of a worm 26 coupled to the
extension of the motor shaft 20, a worm wheel (not shown) in mesh
with the worm 26, an output shaft (not shown) leading from the
center of the worm wheel, etc. The shaft is connected to, for
example, a vehicle power window apparatus.
A rotation detector 28 is comprised of a combination of a sensor
magnet 30 provided on the rotatable side and a magnetically
sensitive device (e.g., a Hall device or a Giant Magneto Resistive
(GMR) device (not shown)) provided on the fixed side. By way of
example, the Hall element is mounted on a substrate fixed to the
reducer case 22 or the end bell 18 so as to face the sensor magnet
30 in rotation. The rotation detector 28 is provided with a wiring
to feed a current to the Hall device and extract a signal
therefrom. The Hall device of the rotation detector 28 detects the
magnetic flux that varies according to the relative movement of the
sensor magnet 30 and the Hall device due to the rotation of the
motor and outputs the variation as a pulse signal. This makes it
possible to detect and control the rotational speed and rotational
position of the motor.
(Sensor Magnet Holder)
FIG. 2A is a perspective view of the sensor magnet holder according
to the embodiment, and FIG. 2B is a perspective view of the sensor
magnet holder according to the embodiment viewed in a direction
different from that of FIG. 2A. FIG. 3 is a front view of the
sensor magnet holder according to the embodiment. FIG. 4 is a
sectional view along A-A of the sensor magnet holder shown in FIG.
3. FIG. 5 is a sectional view along B-B of the sensor magnet holder
32 shown in FIG. 3. FIG. 6 is a rear view of the sensor magnet
holder according to the embodiment. FIG. 7A is a side view of the
sensor magnet holder shown in FIG. 3 viewed in direction C, FIG. 7B
is a side of the sensor magnet holder shown in FIG. 3 viewed in
direction D, and FIG. 7C is a side view of the sensor magnet holder
shown in FIG. 3 viewed in direction E.
The sensor magnet holder 32 (hereinafter, referred to as "holder
32" as appropriate) is an annular resin member used to fix the
sensor magnet 30 to the motor shaft 20. The holder 32 includes a
plurality of annular press fitting parts 36 formed with a through
hole 34 in which the motor shaft 20 is press fitted, a holding part
38 provided radially outside the press fitting part 36 and
configured to hold the sensor magnet 30, and a joint part 40
configured to join the press fitting part 36 and the holding part
38.
In the holder 32 according to the embodiment, three joint parts 40
are provided at equal intervals (at intervals of 120.degree. in the
circumferential direction). Each of the joint parts 40 is
configured such that at least a part thereof is deflected by an
external force. The through hole 34 has a circular shape that
conforms to the sectional shape of the motor shaft 20.
The holder 32 configured as described above can be thinner than
otherwise because the press fitting part 36 and the holding part 38
are not aligned in an axial direction Ax of the motor shaft 20.
Further, the holding part 38 is capable of holding the sensor
magnet 30 in a stable manner as a result of the joint part 40 being
deflected. By selecting the shape and material of the joint part 40
as appropriate, the holding part 38 is prevented from biasing the
sensor magnet 30 with an unnecessarily large force.
As shown in FIG. 6, the joint part 40 includes a radial part 42
that extends radially outward from the press fitting part 36, and a
circumferential part 44 that extends in a circumferential direction
from an end of the radial part 42 opposite to the press fitting
part 36. The circumferential part 44 is an arc-shaped arm. In this
way, the joint part 40 can be formed without extending it in the
axial direction Ax. Further, as compared with a case of providing
the joint part 40 extending in the axial direction Ax of the motor
shaft 20, a desired length of the circumferential part 44 can be
secured without requiring an excessive thickness of the holder 32.
The direction in which the parts extend needs not to be
perpendicular to the axial direction of the motor shaft. A slight
inclination (e.g., 30.degree. or less) may be provided.
The circumferential part 44 according to the embodiment includes a
first circumferential part 44a extending in one circumferential
direction from the radial part 42 and a second circumferential part
44b extending in the other circumferential direction from the
radial part 42. In this way, a plurality of holding parts 38 can be
provided for one joint part 40. By increasing the number of holding
parts 38 for holding the sensor magnet 30, the holder 32 for
holding the sensor magnet 30 is prevented from becoming loose or
displaced.
Further, the joint part 40 includes a first joint part 40a, a
second joint part 40b, and a third joint part 40c at different
positions in the circumferential direction and at equal intervals.
The first circumferential part 44a of the first joint part 40a and
the second circumferential part 44b of the second joint part 40b
are spaced apart from each other. Similarly, the first
circumferential part 44a of the second joint part 40b and the
second circumferential part 44b of the third joint part 40c are
spaced part from each other. Further, the first circumferential
part 44a of the third joint part 40c and the second circumferential
part 44b of the first joint part 40a are spaced apart from each
other. In this way, one of the ends of the circumferential part 44
becomes a free end so that each circumferential part can function
as a cantilever spring.
The holding part 38 is provided near the end of the circumferential
part 44. This can increase the amount of displacement of the
holding part 38 due to the deflection of the circumferential part
44. Further, as shown in FIG. 5, the holding part 38 includes a
guide face 38a that comes into contact with the inner
circumferential surface of the ring-shaped sensor magnet 30 as the
holder 32 is mounted to the sensor magnet 30. As shown in FIG. 4,
the guide face 38a is formed at an angle with respect to the axial
direction Ax. Further, the holding part 38 includes a locking part
38b (see FIG. 5) that prevents the holder 32 mounted to the sensor
magnet 30 from being dislocated. The function of the locking part
38b will be described later.
As described above, three joint parts 40 are provided at equal
intervals in the circumferential direction. In this way, the holder
32 can hold the sensor magnet 30 in a well-balanced manner.
Further, the holding part 38 is provided opposite to the radial
part 42, sandwiching the press fitting part 36. This prevents the
plurality of radial parts 42 from being aligned in a line in the
radial direction of the holder 32 (see FIG. 6). The same is true of
a case where a total of 2n+1 (n is an integer equal to or more than
1) joint parts 40 are provided.
The holder 32 is formed with a convex part 46 as a rotation stopper
that prevents the holder 32 from being rotated with respect to the
sensor magnet 30 while the holder 32 is holding the sensor magnet
30. The convex part 46 is provided in the outer circumferential
part of the holder 32 and is an extension of the radial part 42 of
the joint part 40. The convex part 46 may be provided in each of
the three joint parts 40.
(Sensor Magnet)
FIG. 8A is a perspective view of the sensor magnet 30 according to
the embodiment, and FIG. 8B is a perspective view of the sensor
magnet 30 according to the embodiment viewed in a direction
different from that of FIG. 8A. FIG. 9 is a front view of the
sensor magnet 30 according to the embodiment. FIG. 10 is a
sectional view along F-F of the sensor magnet holder shown in FIG.
9. FIG. 11 is a rear view of the sensor magnet 30 according to the
embodiment.
The sensor magnet 30 is, for example, a ferrite resin magnet and
formed as one piece in a desired shape. More specifically, the
sensor magnet 30 is an annular component formed with a space for
mounting the holder 32 at the center. N poles and S poles are
alternately formed on the outer circumferential surface.
As shown in FIG. 8A, the sensor magnet 30 is formed with three
abutting parts 48 at respective edges of an inner circumferential
part 30a near one end face 30b. The abutting part 48 is an
arc-shaped portion protruding from the inner circumferential part
30a toward the center. The relative axial position of the holder 32
and the sensor magnet 30 are defined as a result of a portion of
the holder 32 coming into contact with the abutting part 48.
As shown in FIG. 8B, the sensor magnet 30 is also formed with three
retaining parts 50 at respective edges of the inner circumferential
part 30a near the other end face 30c. The retaining part 50 is an
arc-shaped portion protruding from the inner circumferential part
30a toward the center. The holder 32 is prevented from being
dislocated from the sensor magnet 30 as a result of the locking
part 38b of the holding part 38 of the holder 32 as mounted being
locked by the retaining part 50.
The three abutting parts 48 are formed at substantially equal
intervals and are arranged at the intervals of 120.degree. in the
circumferential direction around the axial direction Ax. Also, the
three retaining parts 50 are formed at substantially equal
intervals and are arranged at the intervals of 120.degree. in the
circumferential direction around the axial direction Ax. Further,
as shown in FIG. 11, the abutting part 48 and the retaining part 50
are arranged so as not to overlap each other in the axial direction
Ax.
As shown in FIG. 8b, the sensor magnet 30 is formed with a concave
groove 52 in the inner circumferential part 30a to prevent the
holder 32 as mounted from being rotated with respect to the sensor
magnet 30. The concave groove 52 is formed to extend from the other
end face 30c of the sensor magnet 30 to the abutting part 48.
(Magnet Fixing Structure)
FIG. 12A is a perspective view of the magnet fixing structure
according to the embodiment, and FIG. 12B is a perspective view of
the magnet fixing structure according to the embodiment viewed in a
direction different from that of FIG. 12A. FIG. 13 is a front view
of the magnet fixing structure according to the embodiment. FIG. 14
is a sectional view along G-G of the magnet fixing structure shown
in FIG. 13.
A magnet fixing structure 100 according to the embodiment includes
the annular sensor magnet 30 and the holder 32 mounted to the
center of the sensor magnet 30. The holder 32 is mounted from the
side of the other end face 30c of the sensor magnet 30. In this
process, the holder 32 is positioned and prevented from being
rotated with respect to the sensor magnet 30, by inserting the
holder 32 such that the position of the convex part 46 of the
holder 32 is aligned with the concave groove 52.
As the holder 32 is mounted, the guide face 38a of the holding part
38 comes into contact with the retaining part 50, causing the
circumferential part 44 to be deflected toward the center of the
holder 32. Subsequently, as the guide face 38a of the holding part
38 gets over the retaining part 50 and the force with which the
retaining part 50 biases the holding part 38 is reduced, the
elastic force cancels the deflection of the circumferential part
44, allowing the holding part 38 to hold the entirety of the sensor
magnet 30 by biasing the inner circumferential part 30a of the
sensor magnet 30. Once the holder 32 is mounted, the locking part
38b has gone over the retaining part 50 so that the holder 32 is
prevented from being dislodged from the sensor magnet 30.
The holder 32 according to the embodiment is configured such that
the press fitting part 36 and the holding part 38 overlap the
sensor magnet 30 when the holder 32 mounted to the sensor magnet 30
is viewed in a radial direction (see FIG. 14). This can realize a
thin magnet fixing structure 100. The holder 32 is also configured
so that the press fitting part 36 and the holding part 38 overlap
each other when the holder 32 is viewed in a radial direction. This
can realize a thin holder 32. It is more preferred that the holder
32 be configured such that the press fitting part 36, the joint
part 40, and the holding part 38 overlap in part or entirely when
the holder 32 is viewed in a radial direction.
The motor 10 with a reducer according to the embodiment includes a
rotor in which the motor shaft 20 is fixed at the center and the
magnet fixing structure 100. The magnet fixing structure 100 is
configured such that the motor shaft 20 is press fitted to the
press fitting part 36 (see FIG. 14). This reduces transmission of a
force generated when the motor shaft 20 is inserted into the press
fitting part 36 to the holding part 38, preventing a crack in the
sensor magnet 30 due to an excessive biasing force.
(Variation)
A description will be given of variations of the sensor magnet
holder. The description focuses on characteristic features and a
description of features similar to those of the above embodiment
will be omitted as appropriate. FIG. 15 is a front view of the
sensor magnet holder according to the first variation. FIG. 16 is a
front view of the sensor magnet holder according to the second
variation.
A holder 60 includes a press fitting part 62 in which the motor
shaft 20 is inserted, a holding part 64 provided radially outside
the press fitting part 62 and configured to hold the sensor magnet
30, and a joint part 66 configured to join the press fitting part
62 and the holding part 64. The joint part 66 is configured such
that at least a part thereof is deflected by an external force.
The joint part 66 of the holder 60 includes a first joint part 66a
and a second joint part 66b at different positions in the
circumferential direction. A circumferential part 68 of the first
joint part 66a and the circumferential part 68 of the second joint
part 66b are joined. This allows a part of the joint part 66 to be
deflected with a relatively simple structure. Further, the holding
part 64 is provided in a region in which the circumferential part
68 of the first joint part 66a and the circumferential part 68 of
the second joint part 66b are joined. As in the case of a sensor
magnet holder 70 shown in FIG. 16, the circumferential parts 68 of
the respective joint parts 66 may be spaced apart from each other.
In this case, a holding part 72 may be provided at the end of each
circumferential part 68.
FIG. 17 is a front view of the sensor magnet holder according to
the third variation. A holder 74 is of a double annular structure
including an outer annular part and an inner annular part. The
inner annular part corresponds to the press fitting part 76 and a
holding part 78 is formed in a part of the outer annular part. The
holding part 78 is a formed as bellows and holds the sensor magnet
30 with a desired biasing force by selecting the thickness and the
number of folds as appropriate.
FIG. 18 is a front view of the sensor magnet holder according to
the fourth variation. The outer circumferential part of a holder 80
is polygonal (octagon) in shape instead of annular. The holding
part 82 is at the apex of the polygon.
FIG. 19 is a front view of the sensor magnet holder according to
the fifth variation. The holder 84 includes a joint part 90 that
joins a press fitting part 86 and a holding part 88. The joint part
90 is configured such that a radial part 92 thereof is
deflectable.
FIG. 20 is a front view of the sensor magnet holder according to
the sixth variation. A plurality of arms 98 that spiral outward
from a press fitting part 96 are formed in a holder 94. The end of
the arm 98 is the holding part. The arm 98 is curved and so is
deflected with a relatively small force. Therefore, the holder 94
can hold the sensor magnet 30, biasing it with a light force.
FIG. 21 is a front view of the sensor magnet holder according to
the seventh variation. A plurality of arms 112 are formed to extend
radially outward from a press fitting part 96 in a holder 110. The
arm 112 is of a linear shape so that a relatively large force is
required to deflect the arm 112. In other words, the holder 110 can
hold the sensor magnet 30 properly.
FIG. 22 is a front view of the sensor magnet holder according to
the eighth variation. Four joint parts 116 of deformable shape are
provided in the outer circumferential part of the press fitting
part 96 in a holder 114. The joint parts 116 are formed as
rectangular frames and are deflected when the frame as a whole is
deformed. Further, one apex of the joint part 116 functions as a
holding part 117. FIG. 23 is a front view of the sensor magnet
holder according to the ninth variation. Three holding parts 120
formed as circular frames are provided in a holder 118.
FIG. 24 is a front view of the sensor magnet holder according to
the tenth variation. A holder 122 is configured by annularly
joining the plurality of holding parts 88 of the holder 84 shown in
FIG. 19. A circumferential part 124 between adjacent holding parts
88 is configured to be deflectable.
The press fitting part, joint part, and holding part of the holders
described above are formed as one piece. Alternatively, a plurality
of members may be combined to form the holder. The holder is formed
of, for example, glass-filled nylon. Alternatively, the holder may
be formed of resin, rubber, elastomer, etc. The through hole 34 of
the holder 32 needs not to be circular in shape but may be
polygonal (non-circular) in shape. For example, the through hole 34
may be square or hexagonal in shape.
Given above is a description of the invention with reference to the
embodiment and variations. The embodiment and variations of the
present invention are not limited to those described above and
appropriate combinations or replacements of the features of the
embodiment and variations are also encompassed by the present
invention. The embodiment and variations may be modified by way of
combinations, rearranging of the processing sequence, design
changes, etc., based on the knowledge of a skilled person, and such
modifications are also within the scope of the present
invention.
* * * * *